Heaving to holds a sailing boat almost without way. This is how the manoeuvre works, how to practise it and why storm tactics belong in sailing school.
The honest answer upfront: heaving to means positioning a sailing boat with the headsail backed, the mainsail eased and the rudder fixed so that it drifts sideways almost without way. The Bodenseekreis district office describes, in its guideline for the Bodensee skipper's licence, the aim exactly like that: the boat should drift sideways without way [1]. With it you gain time, for example to think or to take a break.
Heaving to is a breather, not a parking spot: the boat keeps drifting, only slowly.
This guide describes the manoeuvre for keelboats and yachts in outline. For heaving to in strong wind or in a storm you belong in a sailing school, not in a guide.
The district office describes a close-hauled course as the starting position [1]. You can start the manoeuvre from all courses, but for the beginning you take the simplest. Milestone: the sails stand calmly, the boat has speed.
Start the tack, but do not bring the headsail to the new side. That leaves it backed, that is against the wind. When righting a dinghy, RYA teaching uses the same principle: with the jib backed the dinghy lies hove-to and the crew can help the helmsman [2]. Milestone: the headsail is backed, the boat does not turn further.
The mainsail is eased depending on the boat type [1]. It should no longer pull. Milestone: the mainsail neither flaps wildly nor pulls.
Put the rudder to windward, more or less depending on the type of boat, and fix it [1]. This makes rudder and backed headsail counter each other. Milestone: the boat drifts sideways almost without way.
Release the rudder lock, bring the headsail across and pick up speed. Practise getting under way as much as heaving to. Milestone: you are sailing on course again without surprising the crew.
Practical note: how far the rudder must be put over and how far you ease the mainsail depends strongly on the boat. You learn that on the boat with an instructor.
first practise backing the headsail in very light wind, without fixing the rudder, and watch how the boat reacts. In the second session you ease the mainsail as well and try how far the rudder has to be put over. In the third session you fix the rudder and roughly gauge how fast the boat drifts to leeward. In the fourth session you practise getting under way: release the rudder, bring the headsail across and pick up speed. Do every session with an instructor on board.
Man overboard is one of the most dangerous situations in sailing, and heaving to does not replace a rescue manoeuvre. A review names falls overboard as the cause of 39 to 44 percent of sailing deaths and capsizing of 20 to 40 percent, with up to 73 percent drowning overall [4]. In the practical part of the German powerboat licence, rescuing a person overboard under sail is a mandatory manoeuvre, with two attempts [3].
This guide explains and motivates, but it does not replace supervised training with an instructor.
One more word on proportion (practical note): heaving to is a craft you must have tried on your own boat once. Every boat behaves differently, depending on hull shape, keel and sail cut. After the first session note which rudder position and which mainsail setting worked on your boat, and use that note as the starting point for next time. That turns a textbook manoeuvre into your own.
Make a heave-to break on purpose: in calm weather on open water, heave to, take a three-minute break and try a snack or chart work. Anyone who learns the manoeuvre in calm moments remembers it in rough ones (practical note).
Heaving to means trimming the boat so that it drifts sideways almost without way. The headsail is backed, the mainsail is eased, the rudder is put to windward and fixed [1].
For example for a break, to think, or in a situation in which you need time. Rescuing a person overboard is a separate skill with its own procedure [3]. For strong wind or storm you need training.
Dinghy teaching knows the principle with a backed jib from righting, in which the dinghy comes to a standstill [2]. The settings, however, are different from keelboats; ask your instructor.
The Bodensee guideline lists it as a manoeuvre [1]. In the official German powerboat licence it is not explicitly in the list of manoeuvres [3]. For practice you learn it anyway.
Q-Turn: The Gybe Substitute in Strong Wind So the Boom Does Not Cross Uncontrolled